Rust-preventing lubricant



Fatented Feb. 26, 1952 RUST-PREVEN TING LUBRICANT Lorne W. Sproule and Laurence F. King,

Ontario,. Canada,

Sarnia,

assignors to Standard 011 Development Company, a corporation of Delaware No Drawing. Application April 14, 1949, Serial No. 87,554

7 Claims.

This invention relates to lubricating oils containing rust preventing additives.

In the operation of fleets of vehicles, particularly Army trucks, it has been found that the steel parts of the engine will rust during idle periods. The presence of the rust has been found to cause excessive wear when the vehicles are placed in operation at a later date. It is an object of the present invention to provide a combination of additives which when added to a heavy duty motor oil will provide a lubricant which prevents the rusting of the steel parts during idle periods. It is more particularly an object of the present invention to provide a lubricant which will meet lubricant specifications such as the United States Ordnance Specification 2126, which requires that the lubricant meet certain specifications with respect to engine cleanliness, inhibition of corrosion in the presence of humidity and moisture condensation, inhibition of salt water corrosion, and prevention of corrosion by the acidic products of combustion.

It has been found that sorbitan monoesters, e. g., sorbitan monooleate, or stearate, possess rust preventing characteristics to a certain degree, but the use of these additives alone, even in concentrations as high as 3%, does not provide inhibition of salt water and acid corrosion. It has been found, however, in accordance with the present invention, that if a fatty acid half-ester of propylene glycol or similar dihydric alcohol is employed in combination with a sorbitan monoester, the combination of additives provides adequate resistance to moisture and salt water corrosion and to corrosion due to the acidic products of combustion. Y

More specifically, the sorbitan monoester which is employed in accordance with the present invention is an ester formed by esterifying one hydroxyl group of sorbitan with an aliphatic monobasic acid, whether saturated or unsaturated, containing 16 to 18 carbon atoms. The additive which is to be employed in combination with a sorbitan monoester may be defined as a half-ester formed by esterifying one molecular proportion of a glycol containing 3 to 5 carbon atoms per molecule with one molecular proportion of a fatty acid containing from to 16 carbon atoms per molecule. Thus, a single acid or mixture of acids in which the major portion of the material consists of fatty acids within the range specified may be employed. A very satisfactory material for this purpose is the mixture of fatty acids obtained from coconut oil. In this mixture of acids caproic, lauric, myristic and palmitic acids normally make up at least of the material, the remainder being fatty acids of somewhat lower and higher molecular weight. Oleic acid, the only unsaturated acid, is present in about 2% proportion. The half-ester prepared by reacting one molecular proportion of this coconut oil acid mixture with one molecular proportion of propanediol-l,2 is particularly satisfactory for the purpose of this invention. It is desirable to employ the sorbitan monoester and the glycol-fatty acid ester in concentrations of 0.2 to 3.0% each in the lubricating oil composition. Concentrations containing about 1% of each are generally preferred and are very satisfactory.

In heavy duty lubricating oil compositions it is generally necessary to employ detergent type additives, such as metal sulfonates, metal salts of phenol sulfides, metal alkyl thiophosphates, such as calcium dihexyl dithiophosphate or calcium di-(methylcyclohexyl) dithiophosphate, or other organic compounds containing metals and sulfur and/or phosphorus. The additives of the present invention may be used in the presence of such detergent type additives.

In' the following example will be described a series of tests which were applied to a heavy duty oil composition containing additives of the type described in the present specification, for the purpose of determining whether the oil meets the requirements of United States Ordnance Specification 2126, and, for comparison, tests were made with similar compositions containing only one of the specified corrosion inhibiting additives. It is to be understood that this example is presented in detail for illustrative purposes and is not to be construed as limiting the scope of the invention in any way.

Example carbon steel panels 2" x 3" x in size, previ-- ously dipped in the lubricant, in a humidity cabinet controlled at F. and 100% humidity for 200 hours. The United States Ordnance Specification 2126 requires that one test specimen Should show no rusting, while the other should In the salt water immersion test two steel panels of the type described above, previously dipped in the lubricant, are immersed in synthetic sea water for 20 hours at room temperature. To meet the specification at least one panel shouldv show no corrosion and .the other may show not more than three corrosion spots, none of which may exceed 1 millimeter in diameter.

The acid neutralization test is designed to show the extent to which the corrosion of steel by the acidic products of combustion is prevented by the presence of the lubricant. The test is carried out by dipping two steel panels of the type described above in a 0.1% aqueous solution of hydrobromic acid for not more than 1 second and immediately immersing the panels in the lubricant at room temperature for 60 seconds.

The panels are then removed from the lubricant 3n and exposed to the laboratory atmosphere for 4 hours. No corrosion or staining is allowable under the specification.

The base oil employed in conducting the tests was a mixture of a well refined, solvent extracted Mid-Continent mineral oil distillate of SAE 10 Grade (viscosity (Saybolt) at 100 F.=160; viscosity index-:95) and a mineral oil of similar type of SAE 30 Grade (viscosity (Saybolt) at 210 F.=65; viscosity index=93), and to this was I added in each case 1.5 (dry basis) of calcium petroleum sulfonate and zinc di-(methylcyclohexyl) dithiophosphate as the detergent additive component. The three corrosion tests describedv above were applied to the above composition con- 1 taining no corrosion inhibiting additive and to compositions containing, respectively, 1% and 3% of sorbitan monooleate alone, 1% and 3% of the coconut oil acids monoester of propylene glycol,

and 1% each of the two additives in the same composition. In addition, another series of tests were conducted with a similar composition containing 1% each of the two anti-corrosion additives, the base oil consisting entirely of the oil of SAE 30 Grade. The results of the tests are shown in the following table:

for 36 hours, and that Grade 2 pass a similar test at 280" F. for a similar period of time.

What is claimed is:-

1. A mineral lubricating 011 containing dissolved therein 0.2 to 3.0% of a sorbitan monoester of an aliphatic monobasic carboxylic acid having 16 to 18 carbon atoms per molecule and 0.2 to 3.0% of a glycol half-ester formed by esteritying one molecular proportion of a glycol containing 3 to 5 carbon atoms per molecule with one molecular proportion of an essentially fatty acid material in which the predominating acids are fatty acids containing from 10 to 16 carbon atoms per molecule.

2. A composition according to claim 1 in which the sorbitan monoester is sorbitan monooleate.

3. A composition according to claim 1 in which the glycol is a propanediol.

4. A composition according to claim 1 in which the fatty acid material is the mixture 01 aliphatic acids obtained from coconut oil.

5. A mineral lubricating oil containing dissolved therein 0.2 to 3.0% of sorbitan monooleate and 0.2 to 3.0% of the propanediol-1,2 monoester obtained by the neutralizing of half of the hydroxyl groups of propanediol-1,2 with the mixture of aliphatic acids obtained from coconut oil.

6. A mineral lubricating oil containing dissolved therein 1.0% each of sorbitan monooleate and the half-ester obtained by neutralizing half of the hydroxyl groups of propanediol-1,2 with the mixture of aliphatic acids obtained from coconut oil.

7. A mineral lubricating oil containing dissolved therein 1.5% of calcium petroleum sul- Ionate, 1.5% of zinc di-(methylcyclohexyl) dithiophosphate, 1.0% of sorbitan monooleate. and 1.0% of the half-ester obtained by neutralizing half of the hydroxyl groups of propanediol-1,2 with the mixture of aliphatic acids obtained from coconut oil.

LORNE W. SPROULE. LAURENCE F. KING.

REFERENCES CITED The following references are of record in the file 01 this patent:

Formulae and inspections of engine preservative oils (U. S. Ordnance Specification 2-126) Grade 1-- Grade 1-With Antioxidants Grade 2.-

no antioxidant with antioxidants Formula, Per Cent by Weight:

Mineral Oil S. A. E. 10 (V/l00=l60; V. I.=95) Mineral Oil S. A. E. 30 (V/2l0=65; V. I.=93) Calcium sulphonate (Dry Basis) Zinc Di-(metliylcyclohexyl) Dithiophosphate (Dry Basis) sorbitan Monooleate Prgpydlene Glycol Monoester of Coconut Oil c1 5 Inspections:

Humidity Corrosion Salt Water Immersion Acid Neutralization Engine Test (U. S. Ordnance AXS-1554): (a) Piston Varnish Rating (b) Varnish Rating, Total Sludge Rating, Total Combined Varnish and Sludge (c) Bearing Weight Loss, G na/Bearing (Aven).

borderline. do

1 With this formulation a gradual separation of some of the propyl In the above table the results of engine tests on the two oil compositions containing both of the corrosion resisting additives are included to Chevrolet engine at oil temperatures of 265 F. 75

one glycol ester additive occurs on standing.

UNITED STATES PATENTS Number Name Date 70 2,386,183 Balcar Oct. 9. 1945 2,398,193 Sharp Apr. 9, 1946 2,417,876 Lewis et al Mar. 25, 1947 .4 .604 Wesson et a1 June 28. 1949 

1. A MINERAL LUBRICATING OIL CONTAINING DISSOLVED THEREIN 0.2 TO 3.0% OF A SORBITAN MONOESTER OF AN ALIPHATIC MONOBASIC CARBOXYLIC ACID HAVING 16 TO 18 CARBON ATOMS PER MOLECULE AND 0.2 TO 3.0% OF A GLYCOL HALF-ESTER FORMED BY ESTERIFYING ONE MOLECULAR PROPORTION OF A GLYCOL CONTAINING 3 TO 5 CARBON ATOMS PER MOLECULE WITH ONE MOLECULAR PROPORTION OF AN ESSENTIALLY FATTY ACID MATERIAL IN WHICH THE PREDOMINANTING ACIDS ARE FATTY ACIDS CONTAINING FROM 10 TO 16 CARBON ATOMS PER MOLECULE. 